Browsing by Author "Barnes, Melanie (TTU)"
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Item Bioaccessibility of antimony and other trace elements from lead shot pellets in a simulated avian gizzard environment(2020) French, Amanda D. (TTU); Shaw, Katherine (TTU); Barnes, Melanie (TTU); Cañas-Carrell, Jaclyn E. (TTU); Conway, Warren C. (TTU); Klein, David M. (TTU)Many studies have used grit (in the form of lead (Pb) pellets) presence in avian gizzards as an indicator of Pb shot exposure. However, due to nearly complete pellet absorption in gizzards or rapid passage of pellets, the absence of Pb shot presence in a gizzard does not confirm lack of Pb shot exposure. This study provides the basis for an additional technique to identify if elevated tissue Pb concentration is due to Pb shot exposure. Bioaccessibility of Pb and trace elements (Sb, As, and Sn) present in Pb shot were quantified to determine if any of these elements would be useful as a secondary marker of Pb shot exposure. An avian physiologically based extraction test (PBET) was used to determine pellet dissolution rate and bioaccessible concentrations of Pb, Sb, As, and Sn in a simulated gizzard environment. Of the three trace elements, only Sb concentrations (44–302 μg/mL) extracted into the gizzard solution were greater than environmental background levels (US soil average 0.48 μg/g); thus, no natural source likely provides this amount of Sb. Therefore, there is evidence that Sb can be extracted from Pb shot in bird gizzards at detectable concentrations (above natural background). While further studies are needed to delineate the mechanisms of absorption and distribution, this study lends credence to the hypothesis that Sb may be a useful marker of Pb shot exposure in biological tissues, particularly when Pb pellets are not present nor observed in avian tissues.Item Enhanced adsorption behaviors of Co2+ on robust chitosan hydrogel microspheres derived from an alkali solution system: kinetics and isotherm analysis(2018) Hou, Tianyu; Zhang, Hongjiao; He, Dongliang; Liu, Qingye (TTU); Zhang, Zhijun; Xiao, Longqiang; Li, Wei (TTU); Barnes, Melanie (TTU)Chitosan hydrogel microspheres derived from the LiOH/KOH/urea aqueous system demonstrate great characteristics of high mechanical strength, relative chemical inertness, renewability and 3-D fibrous network, making them promising functional supports. This work aims to investigate the tunable Co2+ adsorption behaviors on these robust chitosan microspheres in detail, providing the theoretical basis for optimizing the preparation procedure of chitosan microspheres supported Co3O4 catalysts in the future. The experimental results revealed that the fabricated original chitosan microspheres with more extended chain conformation could display enhanced adsorption capacity for Co2+ at determined concentration both in water and alcohol solutions, which is about 2-7 times higher than that of the conventional chitosan hydrogel microspheres prepared from the acetic acid solution. The kinetic experiments indicated that the adsorption process in water solution agreed with the pseudo-second-order kinetic equation mostly, while the chemical and physical adsorptions commonly contribute to the higher Co2+ adsorption on chitosan microspheres in alcohol solution. Moreover, in both cases, the film diffusion or chemical reaction is the rate limiting process in the initial adsorption stage, and the adsorption of Co2+ on chitosan microspheres can well fit to the Langmuir isotherm. Thermodynamic analysis demonstrated that such adsorption behaviors were dominated by an endothermic (ΔH° > 0) and spontaneous (ΔG° < 0) process.